More injection moulding design advice - 6 tips for achievable designs

If you need mouldings to have tight tolerances, don't specify too many, as this will be very difficult to achieve consistently. Due to the vast range of material types & grades available, it isn't practical to suggest a single tolerance level for all types of mouldings & materials.

However, BS7010:1988 provides help on tolerances achievable for each material type & is available to view or buy from BSI's web site - we mostly exceed these tolerances with correct tool design &/or optimisation.

As a guide, if features on your CAD model are not reproduced on the sla / sls models they are probably too small or delicate & it is extremely unlikely that the injection moulding process will be able to make them. Thus, before having the tool made, ensure you increase the size or thickness of these features.

Unless absolutely necessary, avoid undercuts and holes in the side of parts, as this will mean that the mould tool will need expensive side action parts in order to produce them in the moulding.

Should you need to have a textured surface on your mouldings, allow 3 - 5° draft angle to enable the mould tool to be made so that the mouldings can be easily extracted from the tool cores or cavities.

If you want text or logos on your parts, consider how important this is & allow enough room on your part. An inexpensive way, is to get the text/logo engraved on the tool, as this only needs to be paid for once for it to appear recessed or stood up on your moulding. For a more professional, eye catching design, the text or logo can be hot foil or pad printed onto your parts after moulding in a range of different colours.

If possible, design parts like Shaver Plugs so the 2 Case Halves can be moulded & then screwed or snap fitted to the Connector afterwards. This is quicker & more cost effective than designing the Shaver Plug so the Connector needs to be loaded into the tool by an Operator to make the finished Plug.

Moulding design advice - Design flow chart

↱

order & part drawings

KEY & NOTES :-

↑

↓

Yellow

= Start / Endpoint

↑ ↱

design tool

Green

= Process

↑ ↑

↓

Orange

= Decision Point

↑
↑ (No)

design approved ?

↑

(Yes) ↓

Please use this moulding design flow chart as an
overview of the stages of moulding design